In the area of applied electrochemistry, different design electrolyzers have been used for water treatment or for obtaining washing and disinfecting solutions.
A device with flat perforated electrodes pressed against the diaphragm is used for water treatment in the anode chamber and cathode chamber separately. See the Author's Certificate USSR No. 882944 (1978). One of the disadvantages of such a device is the poor hydrodynamics. Another disadvantage is that the resulting products from the anode electrochemical reaction and the cathode electrochemical reaction can become mixed together because the diaphragm has a high penetrability. Also such an electrolyzer containing flat electrodes requires excessive manual labor in order to be assembled and repaired.
Another device for the electrolysis of water consists of a cylindrical electrolyzer with coaxial electrodes which are fixed in dielectric bushings and a diaphragm is placed between the electrodes. The diaphragm separates the inter-electrode space in the cathode and anode chambers. See Japanese Published Patent Application No. 1-104387 (1989). Each chamber has a separate inlet in the lower bushing and a separate outlet in the upper bushing of the electrolyzer which are connected to the pressurized water line. The device includes a power supply connected to the electrodes through the switchboard for changing the polarity of electrodes, for descaling of the cathode electrode and for switching the hydraulic lines which provide the solution output from the anode chamber and the cathode chamber without mixing of the resulting solutions. It is possible to obtain electrochemical processed water with biocide characteristics by using this device.
The disadvantage of this device is the high energy consumption required for water treatment, in particular for the treatment of water which is changing its mineralization during the treatment. The broader the range of mineralization change attempted, the more powerful must be the power supply.
The device that is closest by the technical design and achieved result to the present invention is the apparatus for electrochemical treatment of water discloses in U.S. Pat. No. 5,427,667 (Bakhir et al.), which is a prototype from which the present invention evolved. The device disclosed in this application contains at least one electrochemical cell. The cell contains vertical coaxial cylindrical and rod electrodes and a diaphragm, each of which are made from material which is nonsoluble during electrolysis. The electrodes are installed in dielectric bushings. An ultrafiltration ceramic diaphragm, the main ingredient of which is zirconium oxide, is installed in the bushings between the electrodes. The ability to change the geometric dimensions of the cell is limited by the formula.
The cells are fastened in the lower and upper collectors which are made from dielectric material. The collectors have channels for incoming and outgoing solutions. The cells are installed in the collectors in parallel hydraulically and in parallel or in series--parallel electrically.
The electrodes of the cell are connected with the poles of the power supply in such a way that the cylindrical electrode is an anode and the rod electrode is a cathode. Both electrode chambers are connected with the incoming water in a parallel manner and the cell has flow regulators on both lines. The device also has a water-jet pump for dosing a reagent entered from the tank installed on the water supplying line. The device may include a catalytic chamber. The power supply connected to the electrodes through the switchboard. The anode treated solution is a disinfectant and the cathode treated solution is a washing solution. The disadvantages in using this device for water treatment are that it requires relatively high power consumption and a large number of reagents to clean the cells.
The object of the present invention is to provide an improved apparatus for electrochemical treatment of water that reduces power consumption and extends the functional abilities of the earlier devices. This is achieved by varying the parameters of anolyte and catholyte, in particular by increasing the biocide characteristics of anolyte and reducing its corrosion activity.
This object can be achieved when the device for obtaining washing and disinfecting solutions by the electrolysis of sodium chloride water solution contains at least one electrochemical cell. The cell contains vertical coaxial cylindrical and rod electrodes made from material that is nonsoluble during electrolysis, and a coaxial ceramic ultrafiltration diaphragm. The cylindrical and rod electrodes are installed in the dielectric bushings. The ceramic ultrafiltration diaphragm is installed in the bushings between the electrodes. The diaphragm separates the inter-electrode space into two chambers.
Lower and upper bushings have channels for the treated solution that is supplied into and is discharged from the electrode chambers. The device also contains a metering pump for introducing sodium chloride to the treated water. The water line has a flow regulator which is connected to the metering pump. The poles of the power supply are connected to the electrodes. The feeding line is connected to the inlet of the negative electrode chamber. The outlet of the negative electrode chamber is connected to the inlet of the positive electrode chamber by a special line which has an adjustment for discharging part of the degasified processed solution from the chamber of the negative electrode. In addition, a chamber with catalyst can be installed on the special line. The catalytic chamber may contain a mixture of carbon and manganese oxide and has an inlet in the upper part and an outlet in the lower part. The adjustment for discharging part of the degasified processed solution is executed, for instance, as a separator with the tangential inlet containing a valve which permits the discharge of part of the flow and, after degasification, sends it to the end user. The adjustments for supplying and discharging the treated solution are made as collectors which permits the joining of two or more cells.
It is a known method when the treated solution is consequently passed first through the cathode chamber and then through the anode chamber. See, for instance, Inventor's Certificate USSR No. 865829 (1980). The order of water flowing through the electrode chambers is defined by the requirements for the purification rate from the ions of heavy metals. The regulation of the processes, which are ongoing in the electrode chambers, is aimed of changing the pH of the treated solution. These changes are significant in comparison with the initial solution. In particular, the pH of the solution treated in the cathode chamber is changed so that the treated solution produces a high alkaline reaction which exceeds the pH value for the hydrate formation. In order to obtain a neutral pH, after the filtration of the nonsoluble hydroxides, the acidification of the cathode treated water in the anode chamber is required.
With the new device of the present invention, it is essential that the cathode treated solution together with hydrogen flows through the anode chamber. Regulation of the pH is not so important due to the small value pH changes achieved. The main results from the process are the reduction-oxidizing (Red-Ox) reactions taking place on the surfaces of electrodes and in the volume of the solution. Red-Ox reactions permit the producing of washing and disinfecting solutions with the required characteristics.